1. Field of the Invention
This invention pertains to water-compatible resinous compositions consisting essentially of one or more polymers bearing carbamoylpyridinium groups attached to the polymer through the ring nitrogen and which bears at least two active hydrogen attached to the molecule in combination with an acid curable cross-linking resin. This invention further pertains to the use of said compositions in forming aqueous dispersions and to the use of such aqueous dispersions in coating articles.
2. Description of the Prior Art
Aromatic heterocyclic amines have one (or more) nitrogen atoms as a member of a heterocyclic aromatic ring. Such aromatic amines are normally 5- or 6-membered rings. The 6-membered mononuclear heterocyclic ring systems containing one nitrogen atom are by far the more common and are generally referred to as pyridines. Among the pyridine compounds are the substituted pyridines. Such substituted pyridines include the carbamoylpyridines, with which the present invention is concerned. Like other pyridines, the carbamoylpryidines can be alkylated to form pyridinium salts, i.e., carbamoylpyridinium salts. The carbamoyl group ##STR1## may be attached to the ring carbon atom in the 2, 3 or 4 position.
In electrodeposition, the electroconductive article to be coated is used as either the anode or cathode submerged in an electrocoating bath. The article is coated when a voltage of sufficient magnitude is applied to cause the ionic coating in the bath to migrate to, and deposit upon, the article to be coated. In cathodic electrodeposition, the article to be coated is used as the cathode and the ionic polymer is positively charged. The usual cationic polymers contain basic nitrogen groups in the form of amino groups or quaternary ammonium groups. Typically, the polymers must be cross-linked to develop desirable properties and are normally formulated with cross-linking resins. The acid catalyzed cross-linkers such as the amine aldehyde resins are highly advantageous but do not provide adequate cure for resins containing basic nitrogen. The blocked isocyanate resins were developed to provide acceptable cure for these systems. In electrocoating, it is desirable that the charged resin particles deposit readily and uniformly over the surface of the article, (including the inner or hidden surfaces as well as the exterior surfaces) and coat the article in such a manner as to stop the flow of current. The ability to coat the inner or hidden surfaces is described in the industry as "throwing power." Throwing power is routinely determined in the laboratory and in commercial baths by standard techniques to determine effectiveness of the bath. The higher the throwing power, generally the better. (Journal of Coatings Technology, Vol 53, No. 672, January 1981, pages 52-67, Percy E. Pierce, "The Physical Chemistry of the Cathodic Electrodeposition Process," especially pages 63-66.)